Process for the production of tropone



PROCESS FOR THE PRODUCTION OF TROPONE Genshun 'Sunagawa, 3-85 Omiyamae, Suginamiku,

Tokyo, Japan; Nobuo Soma, 468 Ogikubo, Suginamiku, Tokyo, Japan; and Hideo Nakao, 302 Tsurumicho Toyooka, Tsurumiku, Yokohama, Japan No Drawing. Filed Aug. 19, 1959, Ser. No. 834,676

Claims priority, application Japan Aug. 30, 1958 2 Claims. (Cl. 260-586) The present invention relates to a process for the production of tropone, and more particularly, to the process for the production of tropone by oxidation of 1,3,5- cycloheptat-riene.

Several processes for the production of tropone, for example, a process for producing the same from cycloheptanone and that from 1,3,5-cycloheptatriene are higher to known. These processes, however, cannot be an industrial one. A process for the production of tropone from cycloheptanone is reported by T. Nozoe et al., for example, in The Science Reports of the Tohoku University, First Sedies, vol. 36, 174 (1952), and vol. 39, 170 (1956). According to said process, cycloheptanone is at first subjected to bromination followed by dehydrobromination on heating. The tribromotropone thus obtained gives tropone on catalytic reduction (with palladium). The reaction in this process is scientifically an important one in preparation of seven-membered ring compounds but total yield of tropone in said process is only 30% of the theoretical yield. In addition, in said process are required a large amount of bromine and extremely long period of reaction time. Further, it is disadvantageous that bromine once introduced must be removed by catalytic reduction.

-A process for the production of tropone from 1,3,5- cycloheptariene is reported by W. Doering, for example, in Journal of the American Chemical Society, vol. 76, 3202 (1954), and vol. 79, 352 (1957). According to said process, 1,3,5-cycloheptatriene is subjected to bromination to give dibromotropilidene which is then heated under reduced pressure to give tropiliurn bromide. Said bromide is converted to methoxycycloheptatriene with sodium methylate and said methoxycyloheptatriene is then brominated to give dibromomethoxytronilidene followed by heating under reduced pressure to give tropone. The total yield of tropone from 1,3,5-cyclheptatriene in this process is only 11-17% of the theoretical yield. In addition, this process is so complicated that it involves a number of steps. Therefore this process is also industrially disadvantageous.

The object of this invention is to provide an industrially advantageous process for the production of tropone from 1,3,5-cycloheptatriene, which can be easily carried out and gives a good yield of tropone without being accompanied by the disadvantages of the known processes de-- scribed above.

According to the present invention, aforesaid object can be accomplished by subjecting 1,3,5-cycloheptatriene to oxidation in an aqueous organic solvent with selenium dioxide.

If 1,3,5-cycloheptatriene can be directly converted to tropone by oxidation, tropone may be obtained in only one step, so that the process is an industrially extremely advantageous one. The oxidation of 1,3,5-cycloheptatriene by conventional means would be apt to be accompanied by rearrangement of the ring system with the result of formation of benzene nucleus. For example, if 1,3,5-cycloheptatriene is oxidized with mercury oxide or 2,964,566 Patented Dec. 13, 1960 2 chromic anhydr'ide, benzaldehyde 6r benzoic "acid is produced and no tropone is obtained. We have found that, in the oxidation of 1,3,5-c c1oheptatriene for the preparation of tropone, the use of selenium dioxide leads to the formation of tropone without the rearrangement of sevenmembered ring.

We have further found that in carrying out the process of the present invention the reaction may be effected in aqueous organic solvents such as, for example, a mixture of water and acetic acid, a mixture of water and dioxane, aqueous propanol or aqueous butanol but in view of the procedures involved and the yield obtained it is advantageous to employ as the reaction medium a mixture of water and acetic acid or a mixture of water and dioxane. When the reaction would be carried out in aqueous propanol or in aqueous butanol, byproduct hardly separable from tropone would be produced and the yield of tropone would be low. The above-mentioned disadvantage may be overcome by the use of a mixture of water and acetic acid or a mixture of water and dioxane. The .proportion of water and the organic solvent employed may be conveniently settled by those skilled in the art in such a manner that the resulting mixture dissolves both selenium dioxide and 1,3,5-cycloheptatriene. The reaction may be efiected at room temperature or at elevated temperatures up to boiling point of the reaction medium but it is preferable in view of the reaction velocity to carry out at temperature between about 70100 C. After completion of the reaction, metallic selenium is removed by filtration and the desired product tropone may be recovered from the filtrate by any known process. For example, after completion of the reaction, the reaction mixture is filtered to remove selenium, the solvent is distilled off from the filtrate, the residue is extracted with ether, the ether is distilled off from the ether extract and the residue is subjected to the distillation under reduced pressure to obtain tropone.

The present invention will be illustrated in detail by way of examples.

Example 1 A mixture of 10 g. of 1,3,5-cycloheptatriene, 10 g. of selenium dioxide, 40 cc. of glacial acetic acid and 5 cc. of water is heated with stirring at the temperature of 70 C. for 30 minutes in the atmosphere of nitrogen gas. After cooling, selenium formed is removed by filtration. Acetic acid is distilled off from the filtrate under reduced pressure of 60-70 mm. Hg. The residue is extracted with three portions of 15 cc. of ether. The combined ether extract is dried over magnesium sulfate and the ether is then distilled ofi. The residue thus obtained is subjected to distillation under reduced pressure to give a fraction boiling at 100-105 C./ 10 mm. Hg. Picrate MP. 103 C. Mixed melting point by admixture with authentic tropone picrate is not depressed. The yield is about 30%.

Analysis.--Calculated for C7H60.C6H3N307I 46.57%; H, 2.71%; N, 12.54%. H, 2.92%; N, 12.56%.

Found: C, 46.61%;

Example 2 A mixture of 10 g. of 1,3,5-cycloheptatriene, 12 g. of selenium dioxide, cc. of dioxane and 8 cc. of water is refluxed with stirring for 3 hours in the atmosphere of nitrogen gas. After cooling, selenium formed is removed from the reaction mixture by filtration. The dioxane is distilled off from the filtrate under reduced pressure of 60-70 mm. Hg. The residue thus obtained is treated in the same way as in Example 1 whereby a fraction boiling at -105 C./ 10 mm. Hg is obtained. Picrate M.P. 103 C. Mixed melting point by admixture with a w '4 authentic tropone picrate is not depressed. The yield 2. A process claimed in claim 1 wherein oxidation is is about 42%. eifected at the temperature of about 70100 C.

What we claim is: 1. A process for the production of tropone which come References Cited in The file of this P prises oxidizing 1,3,5-cyc1oheptatrieme with selenium di- 5 oxide in a reaction medium selected from the group con- UNITED STATES PATENTS sisting of a mixture of water and acetic acid and a mixture 1,974,727 Schwenk et 'a1 Sept. 25, 1934 of water and dioxane. 2,831,906 Winberg Apr. 22, 1958 

1. A PROCESS FOR THE PRODUCTION OF TROPONE WHICH COMPRISES OXIDIZING 1,3,5-CYCLOHEPTATRIENE WITH SELENIUM DIOXIDE IN A REACTION MEDIUM SELECTED FROM THE GROUP CONSISTING OF A MIXTURE OF WATER AND ACETIC ACID AND A MIXTURE OF WATER AND DIOXANE. 